import re
from typing import Tuple


def get_granularity(freq_str: str) -> Tuple[int, str]:
    """
    Splits a frequency string such as "7D" into the multiple 7 and the base
    granularity "D".

    Parameters
    ----------

    freq_str
        Frequency string of the form [multiple][granularity] such as "12H", "5min", "1D" etc.
    """
    freq_regex = r"\s*((\d+)?)\s*([^\d]\w*)"
    m = re.match(freq_regex, freq_str)
    assert m is not None, "Cannot parse frequency string: %s" % freq_str
    groups = m.groups()
    multiple = int(groups[1]) if groups[1] is not None else 1
    granularity = groups[2]
    return multiple, granularity